When In Doubt Just Ram Them! The XP-79

Necessity is the mother of invention as the saying goes. In this case that would lead to some very unusual design decisions and ultimately another prototype for the pile.

Messerschmitt ME 163 Komet

[image credit – @2011 Wayne Moyer]

Towards the end of World War Two several rocket powered fighters made an appearance. The most notable was the ME-163 Komet, that would serve as an excellent point defense fighter except for a few problems such as it’s ability to kill its own crew nearly as well as the enemies. The American military watched this from afar with great interest and decided that they needed one of these for their very own.

In a time of war the US Military knew there were two safe bets to look towards. First was Howard Hughes but he was off having his own issues with the Spruce Goose which left one other. Jack Northrop was a brilliant engineer who was fascinated by flying wings and throwing away everything in the book that was thought to work. He would truly start with a blank sheet of paper and build up from there.

At this point in the war the various armies understood the need for a point defense fighter. Where an interceptor or bomber destroyer are designed to spend some time loitering around looking for their target this one did not. The fuel endurance of the ME-163 was around six minutes at which point it would become a glider and a wonderful target for the planes who it just embarrassed.

Understand that it could get to 30,000 feet in one minute from the time of launching. When a bomber stream surprises you, time is not a luxury you have. So time to target is very important. The Russians and Japanese both had rocket fighters in development whose job was the same as the little Komet’s. Neither of these were ever put into production since this was on the bleeding edge of technology of the time.

Which leads to the contract being handed over to Northrop in 1942 for a rocket powered point defense interceptor. It was to powered by new engine called a rotojet but this engine never made it past the prototype stage itself. In 1934 the XP-79 was converted to use two new Westinghouse jet engines of 1150 pounds thrust each. The little fighter weighed in at less then two tons and this would be plenty of encouragement for it to get to speed.

Of note are several features of this design. First is that it was built using a magnesium structure to reduce it’s weight. This gave the little aircraft an unusually strong set of wings. The next unusual feature was placing the pilot in the prone position using a tiller instead of a normal flight stick. This would allow him to withstand 20g’s instead of the normal nine or so that a sitting pilot can withstand.

Next up you will see the bellows on the wing tips. These were boosted and replaced the standard ailerons for the aircraft. Last is the unusual four point landing gear which was necessitated by the size of the aircraft and the placement of the pilot. All of these together led to one of the most advanced and unusual aircraft of it’s time. One last point here that will answer the title of this article. When the pilot ran out of his fifty caliber ammunition he was to be instructed to use the XP-79 as a battering ram to remove the tail of an enemy aircraft. It was believed that the plane was strong enough for this. This design feature was never tested.

During an early test flight a pilot was killed while ejecting from the aircraft. The cause of the accident was never found and it was cancelled pretty quickly thereafter. In the time of war many unusual designs are tested and funded with most of them failing. There is always that chance that you will bat one out of the park and Northrop would try that here and with the B-35 Flying Wing. Unfortunately, also in a time of war, new and untested never usually fares well because to many corners are cut.

The idea of a point defense fighter would end after the second World War. Its premise was sound and very quickly it was found that that missiles would be able to do the same job. There were several attempts at reviving the concept but the time was over and the surface to air missile would be king.

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1302515 comments to http%3A%2F%2Fatomictoasters.com%2F2012%2F04%2Fwhen-in-doubt-just-ram-them-the-xp-79%2FWhen+In+Doubt+Just+Ram+Them%21+The+XP-792012-04-02+15%3A00%3A05Fodderhttp%3A%2F%2Fatomictoasters.com%2F%3Fp%3D13025When In Doubt Just Ram Them! The XP-79

Its more like 27,000 feet per min with an 8.5 min total burn time (or is it flight time back to the books i guess) for the 163B. To be sure ill go look it up in my book. The springs were too stiff on the pilots seat. And I believe that when it occurred the skit had failed to deploy… However many pilots did suffer back injury's.

Well the seat as originally built did not have enough give. SO, when you landed and then seat went down to the bottom and stopped it was your spine that compressed… And that with the skid working and the pilot coming in too fast and too hard. Now if the skid fails and the pilot comes in as slow as possible he can still be injured due to the elimination of the skid to give some absorption of the landing. The early seats had springs that were too stiff but I need to go back and look at the books to see what it is they did to fix the issue… But I think it was a more layered approach with a series of softer to harder springs… at least that is what I would do.

The seat was just one of many problems to overcome with the 163A and 163B.

From the pedia that is a wiki: "The AT-21 proved to be unsuitable for use as a trainer due to vibration and oscillation tendencies as well as an inherent instability caused by the short distance between the rudders and the gull wing resulting in unacceptable yaw even when slight rudder movements were made.[5]

Not deemed suitable for its original purpose, The AT-21 was evaluated as an advanced pilot trainer. This did not work out well, due to poor single-engine performance and multiple gear problems. The aircraft was withdrawn from service in 1944 and was replaced by training examples of the actual aircraft in which the gunners would eventually serve. Many of the AT-21s were then relegated to target-tow duties."

I saw it in the wiki and remember reading about it's final role when i was researching Project Aphrodite a few weeks back. Fairchild gave up on them being piloted and decided to turn them into aerial torpedoes to use against hard targets. This didn't work either.

I think the Komet was actually supposed to make its attack passes (or at least the last one) unpowered before gliding back to base. Given the hideously corrosive hypergolic fuels they used, landing it with any fuel on board would be inadvisable…

Yes indeed the Komet would do two or three passes before it's speed had bled down to far. The six minutes of fuel it carried allowed it to go farther the most would have suspected. Not hard when you are doing 600mph and your target might be at 200mph.

There is even a case of a ME-163 dogfight. I believe it was fighting a Mosquito and did a full power on dogfight. I believe the ME-163 won but I need to go look up the specifics.

It also had a throttle on the rocket engine. Idle. Mid throttle which was I think about half thrust… (I'll go look it up) and Full throttle.
It could do between 1 and 3 passes before running out of ammo.
After the first pass its all on momentum and by swooping down and gaining speed and then climbing back up to attack…